Ypres is a real contender, yep. There are come battles in 1915 where the Germans murdered thousands of attacking French poilus that were trying to take their high ground positions.
But I believe that Somme was the Mother of all Butcherings...

An appeaser is one who feeds a crocodile, hoping it will eat him last. Sir Winston Churchill

Karl, may be I have read that Verdun was fought because the Germans thought "there were too many soldiers in the front", and wasting them in battle was a way of getting rid of them? If that is truth, this is the bloodiest battle, fought to no strategic plan and nothing to be won from its loses.

Verdun, as the "battle" of the Marne, are now subject to new investigations. There is a book called "The myth of the First World War" by John Mosier.
Many things that you have heard came, as obvious, from the "winning" side including French propaganda. Nowadays there is no so much interest in WWI because people are very focused in WW2. But the fact is that Verdun is not what popular gossip tells us. It was a German offensive which main idea was to preempt the allied offensives planned to begin at that time. And it became an attrition battle in which both sides came out heavily damaged. As a matter of fact it was not "a" battle but a series of battles that last many months.
It is claimed as a French victory as the Germans claimed a victory at Jutland. The fact was that the French were uncapable of launching it´s own offensives against the Germans when and where they had intended in the first place.
And they create a hero: Petain.

An appeaser is one who feeds a crocodile, hoping it will eat him last. Sir Winston Churchill

The battles you mention here were protracted - they took place over a considerable period of time. These conflicts are perhaps better seen in the contexts of entire wars.

The concept of the ''bloodiest battle'' is perhaps better examined in the light of short period actions, say over one day, as with battles in pre-modern times.

The bloodiest single day battle I am aware of took place in England - the decisive Battle of Watling Street between the Roman XIV and XX Legions commanded by Setonius Caius Paulinas and the various native English tribes led by Queen Boudicca of the Iceni. This battle, the precise location of which is still unknown, resulted in 400 Roman dead and 80,000 English dead, which substantially eclipses the first day of the Battle of the Somme.

The next bloodiest battle in England was during the War of the Roses, the Battle of Towton, followed by the Battle of Flodden in 1513 between the English and Scots. The Civil War of the 1640's featured relatively light individual battle casualties but the casualties overall were high because of the large number of individual battles the great majority of which were individually of no military significance. Since the two battles in the 1680's - that of Sedgmoor in 1685 and Wincanton in 1688 - both very small battles, there has been no land fighting in England.

Outside the British Isles I am less familiar with what would be the bloodiest of one day battles but no doubt some forum members here could come up with some real horror stories from ancient battles.

In comparison the first day in the Somme looks like a pic nic: the British suffered 19,240 dead, 35,493 wounded, 2,152 missing and 585 prisoners for a total loss of 57,470.
That makes Antietan look small. I wonder why CNN is crying so loud about 3,000 Us casualties in Iraq in 4 years of conflict? OK, a human life is human life, but... look at the numbers. The Romans didn´t pull out their troops nor sued for peace after Cannae: they got pissed and went to Cartage to burn, kick and bite.

An appeaser is one who feeds a crocodile, hoping it will eat him last. Sir Winston Churchill

I wonder why CNN is crying so loud about 3,000 Us casualties in Iraq in 4 years of conflict?

Two factors:

-human life is more valuable now. I think that in the old days (even in the first half of the XX century) illness had taken lot of lifes. As Robert said more people died in the flu than in the Great War. So people was used to the fact that they could died young anyway. Now it is difficult to see a person under 60 years old dying from illness, so seeing young people dead in war is quiet astonishing.

-the Iraq war is totally unreasonable, there was no menace to the US, no mass destruction weapons, no terrorism support. So in the end they are dying for nothing, quiet like in Viet Nam.

Karl, the Roman totals are two estimates by different historians. You can take one or the other but cannot add them together. The Romans took the field with 80,000+ that day, of which 50,000 - 70,000 were killed or captured. Still an incredible total but not what you stated.

Karl Heidenreich wrote:50,000 men dead have to be the record for a single day butchery...

Don't forget the 80,400 dead at Watling Street.

Marcelo,

My understanding is that the Germans used primarily chlorine gas chemical agents, which have since been termed as mustard gas or blister gas, as these agents react with water and attack the skin and tissue in the lungs and orifices.
The Italians used a chemical agent known as impri during their invasion of Abyssinia in 1935-36, some 320 tons of it being declared to the Suez customs authorities while being shipped through the Canal.